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His Master's Noise: A Thoroughly Modern Tube Phono Preamp
His Master's Noise: A Thoroughly Modern Tube Phono Preamp
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Old 24th October 2010, 05:11 AM   #61
jackinnj is offline jackinnj  United States
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His Master's Noise: A Thoroughly Modern Tube Phono Preamp
SY -- where did you park the shield lead from the Sowter 8055's.
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Old 24th October 2010, 10:54 AM   #62
SY is offline SY  United States
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His Master's Noise: A Thoroughly Modern Tube Phono Preamp
On the first stage input ground.

edit: Scratch that, bad memory. On actually looking at it, it's returned to the chassis solder tag at the DIN input.
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Old 24th October 2010, 09:42 PM   #63
volleynbike is offline volleynbike  United States
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Here's a simple little improvement that i've had wonderful results with. Splice in a simple diode (1N4007 or similar) in between the screen grid of the pentode and the Plate with the cathode of the diode pointing toward the screen grid.

Easy to remove if you don't like it. But every pentode amplifier stage i've tried it in shows a marked improvement (extended range, lower dynamic compression, etc.) Admittedly i haven't tried it in such a low level stage as 1st phono, but worth a try...

I've been looking for new mc phono circuit to try, and i think this may be it! Nice job =)
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Old 27th October 2010, 02:25 AM   #64
jackinnj is offline jackinnj  United States
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His Master's Noise: A Thoroughly Modern Tube Phono Preamp
Here's a comparison of the HMN to my Linn LK-1 which has a dedicated MC input:

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Old 27th October 2010, 02:31 AM   #65
Pano is offline Pano  United States
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His Master's Noise: A Thoroughly Modern Tube Phono Preamp
The HMN certainly looks a lot cleaner.
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Old 27th October 2010, 01:26 PM   #66
jackinnj is offline jackinnj  United States
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His Master's Noise: A Thoroughly Modern Tube Phono Preamp
I will have some boards made as a Group Buy -- I'll absorb the cost of the first set of prototypes -- but I have to figure out all the mistakes I made on the first set. Price will be the manufacturing plus shipping to the US. I think it's going to work out to be something like $7.20 per board. The board will have provisioned the amplifier, hv supply, set of regulators (4x) and heater supplies.

Mistakes I made on my prototypes included spacing some of the mosfets a bit close, failing to include take off points for the heaters, building in only one set of HV regulators (SY recommends 2), using a 2A bridge rectifer for the heaters instead of 5A (seems to work fine, however). I'll provision it for various types of caps (Wima, Vishay, etc.) and make it a bit easier to tweak the R and C values for the RIAA equalization.
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Old 1st November 2010, 10:54 PM   #67
studeb is offline studeb  United States
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Interested in boards.
Any feedback from the NJASDIYM?
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Old 2nd November 2010, 12:36 PM   #68
jackinnj is offline jackinnj  United States
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His Master's Noise: A Thoroughly Modern Tube Phono Preamp
Yes, I am going to have some boards made -- it requires a bit of tweaking the original since SY specified 2 regulators -- one per channel. I am not going assume that folks will use transformers with wires rather than PCB pins.

I would think we'll have the boards in about 2 weeks.

I think I will have plenty of power supply boards since folks ask for these all the time, regardless of what they happen to be building!
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Old 2nd November 2010, 03:21 PM   #69
SY is offline SY  United States
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I haven't tried this with a single regulator, but if the pass device is well heatsinked, it should also work- the PSR of the circuit is really high and the current draw is exceptionally constant. Not to discourage you from laying it out as originally designed...
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Old 12th November 2010, 02:14 AM   #70
Slobo is offline Slobo
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I'm also interested in boards.
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